Automatic circuit breaker



Sept. 27, 1938. J SACHS AUTOMATIC CIRCUIT BREAKER 5 Shets-Sheet 1 Filed Jan. 8, 1934 sag Uh s 57 Sept. 27, 1938. J. SACHS 2,131,540

AUTOMATIC CIRCUIT BREAKER Filed Jan. 8, 1954 s Sheets$heet 2 Sept. 27, 1938. J. SACHS AUTOMATIC CIRCUIT BREAKER Filed Jan. 8 1934 5 Sheets-Sheet 5 Sept. 27, 1938. J. SACHS AUTOMATIC CIRCUIT BREAKER Filed Jan. 8, 1934 5 Sheets-Sheet 4 Sept. 27, 1938. J. SACHS AUTOMATIC CIRCUIT BREAKER Filed Jan. 8, 1934 5 Sheets-Sheet 5 Patented Sept. 27, 1938 au'roma'no cmcurr manna Joseph Sachs, West Bartford, Conn., assignor to Colt: Patent Fire Arms Manufacturing Company, Hartford, 001111., a corporation of Connecticut Application January 8, 1934, Serial No. 705,700

82Claims.

I provide a circuit breaker having means additional to the circuit-opening-and-closing contacts-ior normally retaining the movable contact in its engaging or circuit-closing position, and

also having means, electro-responsive or otherwise, for changing the pressure between the two contacts in such a way as to effect the release of. the retaining means and thus permit disengaging or circuit-opening movement of the movable contact. By preference and in accordance with one phase 01 the invention, the retaining means operates automatically and without any associated tripping means so as to permit circuitopening movement of the movable contact whenever the required predetermined change in contact pressure is efiected. This principle may be utilized in a wide variety of ways.

The contact pressure may be changed by means responsive to conditions entirely independent of current conditions in the circuit, as for instance by a device responsive to ambient temperature, or by a fluid-pressure responsive device, or by a speed-responsive device; or the pressure may be changed by a means which is responsive to current conditions in the circuit to be broken. There may be provided various combinations of devices such as aforesaid for changing the pressure, so that the pressure may be changed in the required manner upon the attainment of either 30 of two or more predetermined conditions, as for instance upon the attainment of an excess current condition in the circuit or upon the attainment of. an excess fluid-pressure condition in some container or duct associated with the circuit breaker. When the change in pressure is to be effected upon the attainment of abnormal current conditions in the circuit or upon the attainment of predetermined temperature conditions in the ambient atmosphere, one of the contacts may be mounted upon or connected with a bi-metallic strip which deflects in accordance with current or temperature changes so as to effect the required change in the pressure between the contacts.

Toggle links constitute a simple and inexpensive retaining means which can be biased to an ineiTective position but normally held in eiIective position as the result of the maintenance of at least a predetermined minimum contact pressure; and when a retaining means of. this type is provided, circuit opening is effected by reducing the contact pressure upon the attainment of a predetermined condition.

When there is a handle or operating member included in or associated with the retaining means it may be preferable to provide a means additional to the pressure changing means for eifecting the separation of the contacts, this additional means being so arranged and so related to other parts that the circuit is opened even though the handle or operating member be held in closed-circuit position.

In the accompanying drawings I have shown one principal embodiment of the invention and a variety of alternative embodiments. It will be understood that the drawings are intended to be for illustrative purposes only and are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawings:

Fig. 1 is a front view of a circuit breaker embodying the invention.

Fig. 2 is a view similar to Fig. 1, but showing the front insulating cover removed.

Fig. 3 is a longitudinal sectional view taken along the line 3-3 of Fig. 2 and showing the movable parts in their closed-circuit positions.

Fig. 4 is a fragmentary longitudinal sectional view taken along the line 4-4 of Fig. 2 and showing the movable contacts in open-circuit positions but with the operating handle retained in closedcircuit position.

Fig. 5 is a view similar to Fig. 4 but showing the movable parts about to be automatically released frorri their closed-circuit positions.

Fig. 6 is a view similar to Fig. 4i but showing all of the movable parts in their open-circuit positions.

Figs. 7 to 24 are diagrammatic views illustrating various alternative or optional details of construction, the movable parts in each instance being shown in their closed-circuit positions.

In the drawings, particularly Figs. 1 to 6, I have shown a circuit breaker similar in many respects to that disclosed in my patent for Automatic circuit breaker, No. 2,020,333, dated November 12, 1935. Reference may be had to the said pat cut for features of construction not herein shown and described in detail. This particular circuit breaker has been selected merely as illustrating one type of circuit breaker mechanism to which the present invention is applicable, and it will be understood that in its broader aspects the invention is in no way limited to a circuit breaker of this particular type. The construction shown in Figs. 1 to 6 will now be described, but it will be understood that as to many details there may be wide variation from what is shown.

The circuit breaker has a main insulating base or support I which carries all of the other parts of the circuit breaker. Fitting the support I at the front thereof is an insulating cover 2. The rear support I is of. box-like form, being substantially closed at all foursides and at the bottom. The front cover is also of more or less box-like form, having a recess open at the bottom into which certain parts of the mechanism project. When the two parts I and 2 are assembled as shown, there is provided an interior recess which contains all of the operative parts of the circuit breaker other than the handle.

Carried by the rear support I near the front thereof are two forward projecting parallel metallic plates 3, 3 which are held in place by means of screws 4, 4 extending forward from the rear of the support. The plates 3, 3 are provided with integral rearward extending portions 3. Carried by the said rearward extensions 3 and extending transversely between them is a pivot pin 5. Pivotally mounted on the pin 5 is a contact carrying member which includes two parallel plates 6, 6 spaced apart transversely and suitably connected together to move as a unit.

The two main movable contacts I and 8 are positioned between the outer planes of the two insulating side plates 6, 6 and they are arranged in tandem, that is, they are spaced apart circumferentially. Preferably each movable contact I and 8 extends from one to the other of the two plates 6, 6 and is in direct engagement with both of them. Each of the said plates 6 is provided with a hole 9 and a notch I0 adapted to receive similarly shaped lateral projections on the corresponding contact. When the said projections on the contacts are entered in the said holes and notches of the two plates, the contacts are firmly held in proper predetermined relationship.

The two plates 6, 6 are additionally connected and held in spaced relation by means of insulating members II and I2. The two plates and the insulating members are held in proper relationship by means of tierods or rivets I3, I3 extending through suitable holes. Preferably the plates 6, 6 have arcuate outer edges concentric with the pivotal axis at 5 and the insulating members II and I2 are externally shaped to conform to these arcuate edges. It will be understood that the insulating members II and I2 extend transversely from plate to plate and. that the movable contact 1 extends through the space between the two members. The member I I engages with the other movable contact 8 and thus extends circumferentially from one contact to the other.

The two movable contacts I and 8 are electrically connected with each other, this electrical connection preferably being through an electroresponsive means which is carried by and is bodily movable with the contact member. By preference and as shown, this electro-responsive means is a bi-metallic thermostatic strip I4 mechanically and electrically connected directly with one of the contacts, as for instance the contact I. The strip I4 is provided at its projecting end with an aperture I5 which enables the strip to serve as a latch as will be presently explained. In order to complete the electrical connection between the two contacts I and 8 there is provided a suitable flexing or flexible connection I6 between the strip I4 and the contact 8. The connection I6 is sufliciently flexible to permit the bi-metallic strip I4 to freely deflect or bend under the influence of heat.

Carried by the insulating support I are two substantially stationary main contacts I! and I8. These stationary contacts I! and I8 are so positioned and arranged that they can be firmly engaged respectively by the two movable contacts I and 8 as clearly shown in Fig. 3. It will be apparent that pivotal movement of the contact member serves to bring the movable contacts I .and 8 into or out of engagement with the respective stationary contacts I! and I8 to make or break the circuit. A suitable spring means as shown at I9 is provided for biasing the member in the contact disengaging or circuit-opening direction.

For actuating the contact member for normal switching purposes or to effect closing of the circuit after automatic opening thereof, I may provide an actuating member or actuator 20. This actuator is normally engaged by the thermostatic strip or latch I4, the end of the actuator entering the before-mentioned aperture I5. The actuator is preferably pivoted to the contact member for movement about a bodily movable transverse axis at 2I. As illustrated, the actuator 20 is of hell crank form, and a transverse pin 22 serves to limit relative movement in the counter-clockwise direction. With the parts in the relative positions shown in Fig. 3, the actuator and the contact member are positively connected to move in unison.

For manually operating the actuator 20 I may provide a handle member 23 which is mounted on a pin 24 extending transversely between the supporting plates 3, 3. The handle member projects through an opening in the front wall of the front cover 2, the opening being of suflicient length to permit the necessary movements of the handle. As shown in Figs.'2 and 3 there is provided a spring 25 which serves to bias the handle toward its open-circuit position, that is, in the counter-clockwise direction from the position shown in Fig. 3. The handle member 23 is connected with the actuator 20 by means of a link or links 26, the links being pivoted to the handle member at 2'! and to the actuator at 28.

When the parts are in the relative positions shown in Fig. 3 the links 26 cooperate with the handle member 23 to form a toggle which locks the parts in position with the movable contacts I and 8 pressed into flrm engagement with the substantially stationary contacts I! and I8. Continued movement of the handle in the clockwise direction is prevented by the engagement of an extension 23 thereon with a pin 29 extending transversely between the plates 3, 3. The pivotal axis at 27 is above a straight line connecting the pivotal axes at 24 and 28, and thus the handle member 23 and the links 26 serve to resist the tendency of the contact member to move in the clockwise direction. At the same time the said toggle action holds the handle 23 in its right hand or closed-circuit position, resisting the tendency of the spring 25 to move the handle member in the counter-clockwise direction.

The above-described toggle action can be released by pressing the handle toward the left, the parts then moving under the action of the springs I9 and 25 to the open-circuit positions shown in Fig. 6. The movable contacts I and 8 are thus disengaged from the stationary contacts I! and I8 and the circuit is broken in two separate places. By moving the handle toward the right the several parts can be restored to their respective positions, as shown in Fig. 3, and the circuit can be thus re-established.

It will be evident that the force required for moving and holding the contact member is transmitted through the links 20 to the actuator 20 and from the actuator to the contact member. The normal connection between the actuator and the contact member is partly through the pivot pin at 2| and partly through the thermostatic latch ll. As already explained the bi-metallic strip I4 is electrically connected between the movable contacts I and I. It is adapted to be deflected downward or outward upon the passage of excess current therethrough, with the result that the strip is disengaged from the actuator 20. This disengagement permits the actuator to turn slightly relatively to the contact member and in the clockwise direction. This slight clockwise movement reduces the pressure which had theretofore served to hold the links 26 and the handle member 23 in their effective toggle relationship. This reduction in pressure permits the handle member 23 to move in the counter-clockwise direction so as to render the toggle inefiective, thus freeing both the contact member and the handle member so that they are automatically moved to their open-circuit positions under the influence of the springs I9 and 25. It will be understood that the contact member and the handle member move substantially simultaneously, and that when the parts reach their full open-circuit position, as shown in Fig. 6, the latch I4 and the actuator 20 can freely reengage as soon as the strip II has sufllciently cooled.

The described circuit-opening movement of the contact member is not in any way dependent on the circuit-opening movement of the handle member and will, in fact, occur even though the handle member be held in its closed-circuit position, as shown in Fig. 4. The downward or outward deflection of the thermostatic strip it permits the actuator 20 to turn in the clockwise direction as already stated, thus releasing the contact member from the control of the handle member 23 and of the links 26. The contact member then moves in the clockwise direction to the position shown in Fig. 4, the actuator 20 and the links 26 assuming the relative positions shown. If the handle 23, after having been held as described. be now released, it will move under the influence of the spring 25 to its open-circuit position as shown in Fig. 6, thus bringing the actuator 20 into its normal position with respect to the contact member so that it can be engaged by the latch H,

I have shown and described two pairs of contacts i, i1 and 8, i8, one contact of each pair being movable and the other being stationary or at least substantially stationary. The two contacts engage each other with considerable pressure, and in accordance with the present invention this pressure is utilized in a novel manner. Preferably at least one contact of each pair is mounted so as to yield as pressure is applied to effect normal contact engagement. While I do not so limit myself, I have shown the substantially stationary contact of each pair 'as yieldably or resiliently mounted. The two contacts I! and I8 are carried respectively by resilient supports or strips 3|! and Si which strips are bent or deflected respectively upward and downward as the contacts yield under the influence of pressure applied by the operating mechanism.

I have already stated that the movable contact member with the movable contacts I and 8 thereon is biased in the circuit-opening or contact disengaging direction, and I have already stated that the tendency of the movable contacts toso move is overcome or resisted by the toggle action of the members or links 22 and 28. In accordance with the present invention I utilize the beforementioned pressure between the contacts to hold the toggle links in their eilective locking or hold- :5 ing relationship. The spring I! acting alone is not sufliciently powerful to resist the tendency of the spring 25 to break the toggle action between the members 23 and 28; but the pressure exerted by the contacts I! and it, particularly when combined with the action 01' the spring i9, is suihcient to overcome the spring 25 and to hold the toggle links in their locking relationship. Thus the toggle members or links 23 and 25 constitute a retaining means which resists the bias of the movable contact and which is normally dependent for its effectiveness upon contact pressure resulting from the resilient mounting of the contacts 11 and I8.

Inasmuch as the effectiveness of the beiore-described retaining means is normally dependent upon pressure between the contacts I1, 1 and II, 8, it will be apparent that the said retaining means will automatically become ineffective if the contact pressure be sufficiently changed. Therefore, in accordance with the present invention I provide means, electro-responsive or otherwise, for changing the contact pressure in such a way and to such an extent as to cause the retaining means to become ineffective and to thus release the movable contacts for automatic disengaging movement. The character of the pressure changing means may be widely varied, but the desired result may be very conveniently attained by electro-responsive means, as for in- 35 stance electro-thermally responsive means such as bi-metallic strips arranged to be heated in accordance with the current conditions in the ci-rcuit. I have shown the before-mentioned strips 30 and 3| as being formed of bi-metallic ma-MO terial and arranged to be heated in accordance with the current conditions in the circuit and to be automatically deflected in the directions to reduce the pressure. As shown the strips 20 and II are electrically connected wtih the respective cons45 tacts i1 and i8 so as to form a part of the circuit, and they are arranged to be deflected respectively upward and downward as their temperature increases.

Referring particularly to Fig. 5, let it be sup-r50 posed that a current in excess of a predetermined maximum is passing through the circuit breaker. As the result of this excess current the strip 30 tends to deflect upward and the strip 3| tends to deflect downward. Inasmuch as these stripsJiSii have already been deflected upward and downward as the result of pressure, the result of the heating action is not to actually move the contacts to any considerable extent, but rather to merely reduce the contact pressure. When the= contact pressure becomes sufliciently reduced the spring 25 begins to move the handle member 23 in the counterclockwise direction as shown, thus moving the toggle axis 21 below a straight line connecting the axes 24 and 28 and breaking the toggle. This permits all of the movable parts to automatically move to the full open-circuit position as shown in Fig. 6. It will be observed that this circuit opening action may take place without any disengagement of the latch H from the-l0 actuator 20. As soon as the strips 30 and 3! have sufllciently cooled, the parts may be restored to the normal closed-circuit position as shown in Fig. 3.

While I have shown the substantially sta-IK tionary contacts i1 and I! as electro-responsively acted upon to change the contact pressure, it will be understood that there may be wide variation from this particular arrangement, as will be herematter more fully explained. Considered broadly, it will be observed that I have provided two movable and stationary contact supports, the two plates 6, 8 with their associated parts constituting the movable support and the insulating base i constituting the stationary support. At least one pair of cooperating movable and substantially stationary contacts are mounted on the respective supports and at least one contact of each pair is preferably mounted so as to yield relatively to its support as pressure is applied to effect normal contact engagement. Associated with at least one of the contacts is a pressure changing means which may be an electro-respon sive device operable upon the attainment of abnormal current conditions in the circuit to change the contact pressure in such a way as to cause the retaining means already described to release the movable support for automatic contact disengaging movement.

I do not necessarily rely upon a spring such as I! for biasing the movable contact for disengaging movement; in some instances the spring may be omitted and reliance placed upon the weight of the movable parts, or reliance may be placed on some differently placed spring, as for instance the spring 23. In referring to abnormal current conditions I do not necessarily limit myself to excess current conditions, but I intend to include deficient current or electrical energy conditions such as may occur when the current is entirely cut 01! or when the voltage is reduced below normal.

It will be observed that in the circuit breaker described I have provided two separate electroresponsive means, the bi-metallic strip l4 con stituting one such means and the two strips 30 and SI constituting the other such means. Ordinarily when two separate electro-responsive means are provided it will be deemed preferable for them to have difierent electro-responsive characteristics. For instance, it may be preferable to so design and construct the strip I4 that it is relatively insensible to moderate overload conditions, but is nevertheless almost instantly responsive to extreme overload or short circuit conditions. The strips 30 and 3i may be so designed and constructed as to be slowly responsive to moderate overload conditions without, however, being capable of acting sufliciently rapidly to properly take care of extreme overload or short circuit conditions. With this particular relationship of the two electro-responsive means, the strips 30 and 3| are utilized to take care of moderate overload conditions such for instance as may occur in the starting of a motor and their design and construction is such'that the overload current may be carried for a reasonable predetermined length of time without opening the circuit breaker. If, however, the overload condition is continued beyond the predetermined time the strips deflect sufliclently to reduce the pressure and cause the opening of the circuit breaker in the manner described. If however, extreme overload or short circuit conditions occur, the strip i4 is almost instantly deflected to disengage the actuator and in that way cause the automatic opening of the circuit breaker.

As concerns the action of the strips 30 and 3| the circuit breaker is not handle free and will not open so long as the handle 23 is held in closedcircuit position. However, the other electro-responsive means, that is, the bi-metallic strip l4,

prevents any possible damage to connected apparatus as this will eventually act whenever the excess current conditions become dangerous and will serve to open the circuit breaker even though the handle 23 be held.

In order that the operating characteristics of the circuit breaker may be readily changed, particularly as concerns the moderate overload release, the two bi-metallic strips 30 and iii with the respective contacts I] and I8 thereon, may be so mounted that they can be readily removed as units and replaced by other similar units having different electrical characteristics. As shown, the base I carries wire terminals 32 and 33 from which extend transverse conductors 34 and 35. The outer ends of the respective strips 30 and 3| engage directly with these conductors 34 and 35 and are held in place by means of nuts 36 and 31. It will be obvious that by removing the nuts 36 and 31 the respective units referred to can be removed and replaced.

In the various diagrammatic figures numbered 7 to 24 which will now be described, I have omitted various mechanical details. It will be understood that the details in each instance are or may be as shown in Figs. 1 to 6 and already described, except where different details of construction are described or clearly appear from the Y diagrams.

In Fig. 7 I have shown diagrammatically a construction in which the bodily movable electroresponsive means, such as I4, is entirely omitted, the two movable contacts I and 8 being directly connected by a conductor 38. This considerably simplifies the construction and may be entirely suitable for conditions where a handle free circuit breaker is not required.

In Fig. 7 I have also shown a type of holding or retaining means which is quite different from that shown in Figs. 1 to 6, but which is nevertheless dependent upon the contact pressure or is at least dependent upon the avoidance of a predetermined change in the contact pressure. I have shown a handle 39 pivotally connected with a link 40 which in turn is pivotally connected directly with the movable contact member; but the parts are so related that they have no toggle action. The contact member is held in its closed-circuit position by means oi a lug 4i which engages a detent 42 controlled by a spring 43. The detent 42 serves to hold the contact member in the closed-circuit position so long as no more than a predetermined normal pressure exists between the contacts of the two pairs. The substantially stationary contacts I! and I8 are mounted respectively on bi-metallic strips 44 and 45 which are arranged to be deflected respectively downward and upward upon the attainment of excess current conditions. The result of this deflection of the strips 44 and 45 is to increase the pressure at the contacts instead of to decrease the pressure as described in connection with Figs. 3 to 6; and it will be evident that when the contact pressure is sufliciently increased the movable member with the contacts 1 and 8 thereon will be slowly moved in the clockwise direction until finally completely released from the detent 42. It will be apparent that with the construction shown in Fig. .7 the opening of the circuit is effected by an increase in contact pressure, rather than by a decrease in contact pressure as was described in connection with Figs. 3 to 6.

In Fig. 8 I have shown a retaining means of *nected to form a part oi the circuit.

the toggle type similar to that shown in Figs. 1 to 6, but I have shown only one pair of main contacts instead of two pairs. The movable contact 46 is carried by a conductor 41 which extends to a point near the pivotal axis of the contact member where it is connected with a flexible conductor 49. The substantially stationary contact I! is carried by a bi-metallic strip 49 similar in construction and purpose to the strip 30 shown in Figs. 3 to 6. However, in order to further illustrate the scope oi. the invention, I have shown the contact I! as insulated from the strip 49, and I have shown a separate heating element 50 connected in the circuit and located adjacent the strip 49 so as to effect the heating thereof indirectly. As the strip 49 becomes heated it deflects upward, thus reducing the contact pressure effecting the opening of the circuit breaker in the manner already described in connection with Figs. 3 to 6.

In Fig. 9 I have shown a construction in many respects similar to that shown in Fig. 8, but hav ing a different arrangement for providing resilience of contact mounting. It is not necessary that the bi-metallic strip supporting one of the contacts be highly resilient and under some circumstances it may be found preferable to use a relatively rigid bi-metallic strip and to provide the necessary resilience by other means. I have shown the movable contact 5| as carried by a resilient strip 52 which is secured to the movable contact member. Relative movement of the strip 52 is limited by a suitable stop 53. The substantially stationary contact 54 is carried by a relatively heavy and rigid bi-metallic strip 55 con- When the parts are in closed-circuit position the strip 52 is deflected as shown, and the resultant contact pressure serves to hold the retaining means in effective position. Upon the attainment of excess current conditions in the circuit the bimetallic strip 55 is deflected upward, and the contact 5| moves upward with the contact 54 until limited by the stop 53, whereupon the contact pressure is rapidly reduced so as to release the retaining means and permit the circuit breaker to automatically open.

In Fig. I have shown a construction wherein the movable contact 5| is supported on a resilient bi-metallic strip 56 and wherein the stationary contact 51 is carried by a substantially rigid support 59. Upon the attainment of excess current conditions the bi-metallic strip 56 is deflected downward relatively to the movable contact support, thus reducing the contact pressure. By reason of the rigid mounting of the contact 51 the net result is to permit the movable support to move slightly in the counter-clockwise direction, thus releasing the retaining means and permitting the circuit breaker to open.

In Fig. 11 I have shown a construction wherein both of the contacts are supported on resilient bi-metallic strips. The movable contact 5| is carried by a resilient current-carrying bi-metallic strip 56 as described in connection with Fig. 10, and the substantially stationary contact I! is carried by a resilient current-carrying bi-metallic strip 59, as described in connection with Figs. 3 to 6. It will be evident that with this construction there are two separate electro-responsive means each capable of acting to reduce or otherwise change the pressure between the contacts and to thus cause the circuit breaker to open. The two strips 56 and 59 may be so arranged that upon the passage of excess current they both deflect in the direction to reduce the pressure, the strip 56 deflecting relatively downward and the strip 59 deflecting upward.

In Fig. 12 I have shown a construction illustrating the fact that the thermal electro-responsive means need not necessarily be a bi-metallic strip. The construction is in some respects similar to that shown in Fig. 8, but the substantially stationary contact is carried by and electrically connected with a resilient strip 6| which is not bi-metallic. The said strip 6| is secured to a hub 62 pivotally mounted upon a pintle 63. Surrounding the pintle and interposed between it and the hub is a body 64 of solder, wax or other material which readily melts when the temperature is increased. An extension 63' of the pintle is surrounded by a heating coil 65 connected in the main circuit. So long as the current does not exceed a predetermined maximum the solder prevents the hub 62 from turning and the strip 8i maintains the necessary pressure between the contacts. Upon the attainment of excess current conditions the extension 63 is heated by the coil 65 and the heat is transmitted to the pintle 63 and the solder 64. When the solder melts the hub 62 can turn in the clockwise direction, thus reducing the contact pressure and permitting the circuit breaker to open. A light spring 66 is provided to return the hub 62 to its normal position while the solder is still hot. Thus as the solder cools the hub is rigidly held in the normal posi tion as shown, and the normal contact pressure is obtained when the contacts are reengaged.

In Fig. 13 I have shown a construction i1lus- 'trating the fact that the pressure changing action may be magnetic instead of thermal; and in this same figure I have illustrated the fact that the said action may be either thermal or magnetic according to conditions. The construction is similar to that shown in Fig. 11, but it has an electro-magnet Bl cooperating with an armature 69 on one bi-metallic strip, as for instance the bi-metallic strip 59 which carries the substantially stationary contact l1. As shown the electromagnet 61 is connecteddirectly in the main circuit, but it may be controlled by a thermally operated relay connected in the main circuit, or it may be controlled by entirely independent means as will be hereinafter explained in detail. The two bi-metallic strips 56 and 59 may be connected and arranged to be deflected respectively downward and upward to reduce the contact pressure upon the attainment of excess current conditions. The magnet 61 when sufiiciently energized tends to move the bi-metallic strip 59 upward, and upon the attainment of extreme overload or short circuit conditions the magnet serves to instantly lift the strip 59 and the contact I! so as to cause the circuit breaker to open more quickly than it would as the result of the heating action in the bi-metallic strips.

If preferred the two bi-metallic strips shown in Fig. 13 may be arranged to have diflerent operating characteristics instead of the same operating characteristics. The strip 59 may be arranged to deflect upward to reduce the pressure upon the passage of excess current, thus permitting the circuit breaker to open in the manner described; and the strip 56 may be so arranged that, as the result of the heating efiect of the normal current, it is deflected relatively upward from its free or relaxed position. With this arrangement it is necessary for the circuit breaker, upon being flrst closed, to be manually held long enough to permit the strip 56 to attain a normal operating temperature. By reason of this normal operating temperature the strip 58 is deflected rel atively upward to a sufllcient extent to exert the pressure necessary to maintain the toggle links in effective position. With the two bi-metallic strips 56 and 59 connected and arranged as last described, the circuit breaker operates automatically upon the attainment of either one of two abnormal current conditions. Upon the attainment of excess current the strip 56 is deflected upward and it may be acted upon by the magnet 61, thus reducing the contact pressure and permitting the circuit breaker to open; and upon the attainment of an underload or deficient electrical energy condition in the circuit the strip 56 no longer maintains its normal upward deflection, but bends relatively downward toward its free or relaxed position, thus reducing the contact pressure and permitting the circuit breaker to open.

In Fig. 14 I have shown a circuit breaker having no bi-metallic strips for supporting the contacts and in which the pressure changing action is entirely electro-magnetic. The construction is similar in some respects to that shown in Fig. 8, but differs in that there is no bi-metallic mounting for the substantially stationary contact and in that provision is made for underload operation instead of overload operation. The contact I1 is carried by a resilient strip 69 which is not bi-metallic. The strip 69 is provided with an armature III which is acted upon by an electromagnet H connected in the main circuit. The magnet ll serves to draw the strip 69 downward so as to maintain the necessary pressure at the contacts; but the resilience of the strip 69 is such that it tends to move upward to reduce the contact pressure when it is released by the magnet. It will be apparent that when the circuit breaker is first closed the magnet H is energized and serves to hold the strip 69 in its lower position and to thus maintain the necessary contact pressure. If the current is cut off or if there is otherwise attained a deficient electrical energy condition in the circuit the magnet H is no longer sufficiently energized and the strip 69 movesupward by reason of its own resilience, thus reducing the contact pressure and permitting the circuit breaker to open.

In Fig. 15 I have shown a circuit breaker similar to that shown in Fig. 10, but also having a bodily movable electro-magnet 12 arranged to cooperate with an armature 13 carried by the bimetallic strip 56. This circuit breaker is provided with two pairs of contacts, the contact l8 being carried by a resilient strip 14. The magnet 12 is mounted on the movable contact member and is electrically connected between the strip 56 and the movable contact 8. It will be understood that upon the attainment of moderate overload conditions the action of the circuit breaker will be exactly as already described in connection with Fig. 10. However, upon the attainment of extreme overload or short circuit conditions the magnet 12 will be sufliciently energized to attract the armature l3 and thus substantially instantly move the strip 56 so as to reduce the contact pressure and permit the circuit breaker to open.

In Fig. 16 I have shown a construction similar to that shown in Figs. 3 to 6 with the exception that the resilient strips supporting the contacts I1 and I8 are not bi-metallic. The said contacts H and 18 are supported by resilient strips 15 and l5 provided respectively with armatures l6 and 11. These armatures are adapted to be acted upon by electro-magnets 18 and 19 connected in the main circuit. These electro-magnets I8 and 19 serve upon the attainment of excess current conditions, particularly extreme excess current or short circuit conditions, to move the strips 18 and I5 respectively upward and downward, thus reducing the contact pressure and permitting the circuit breaker to open. The bi-metallic strip I4 will act to open the circuit in the manner already described in connection with Figs. 3 to 8.

In Fig. 17 I have shown another construction similar to that shown in Figs. 3 to 6. However, instead of a bi-metallic latch I4 carried by the contact member and electrically connected in the circuit, I have shown a mechanical latch pivoted to the contact member at 8| and normally held in its operative position by means of a spring 82. Also carried by the movable contact member is an electro-magnet 88 connected in the circuit between the two movable contacts I and 8. The action of the two bi-metallic strips 86 and 3i is or may be exactly as already described in connection with Figs. 3 to 6. The strips may serve to open the circuit upon the attainment of moderate overload conditions. However, upon the attainment of extreme excess or short circuit conditions the magnet. will be energized to draw the latch 80 downward so as to disengage it from the actuator 20 and thus permit the circuit breaker to open in the manner already described.

In Fig. 18 I have shown a construction in which the means for changing the pressure between the contacts is not in any way dependent on the current conditions in the circuit. The pressure between the contacts is changed by a means which acts upon the attainment of a predetermined condition which is entirely independent of current conditions. in the circuit.

In this same figure I have also illustrated the fact that it may not in every case be necessary to provide a special yieldable or resilient mounting for one of the contacts. The construction is in some respects similar to that shown in Fig. 8, but the substantially stationary contact 51 is carried by a rigid pivoted lever 84 normally held by a latch 85. No special resiliency is provided in any of the described parts and the contact pressure for holding the toggle links in place results from such incidental resilience as may exist in the parts themselves and in the bearings and supports. Associated with the latch 85 is an electro-magnet 86 connected to be energized separately from the main circuit. When the magnet circuit is closed, as for instance by a remote switch 81, the magnet is energized to move the latch 85 toward the right, thus releasing the lever 84 and permitting it to move in the clockwise direction. This eliminates the contact pressure and the circuit breaker opens. After opening the springs 88 and 89 return the lever 84 and the latch 85 to their normal positions.

In Fig. 19 I have shown a construction in some respects similar to that shown in Fig. 8. The substantially stationary contact 90 is connected with a flexible conductor 8|, and the said contact is carried by a movable piston rod 92 but is insulated therefrom. Connected with the rod 92 is a piston 93 movable in a cylinder 94. A spring 95 tends to move the piston 93 downward and thus serves to provide the necessary pressure between the contacts 90 and 46. A pipe 96 is connected with the lower end of the cylinder 94 and serves to maintain therein a pressure corresponding to the pressure in some receptacle or system with respect to which pressure control is desired. When the fluid pressure in the system rises above a predetermined maximum there is a corresponding increase in pressure in the cylinder 94 and the piston 99 moves upward in opposition to the spring 95, thus reducing the contact pressure and permitting the movable contact 49 to move to open-circuit position in the manner already described. I have referred to operation of the piston 99 as the result of an increase in fluid pressure, but it will be obvious that by reversing the positions of the spring 95 and of the pipe 96 the piston can be operated to reduce the contact pressure when the fluid pressure falls below a predetermined minimum.

In Fig. 20 I have shown a construction similar to that shown in Fig. 19, but differing in that the device is operated as the result of the change in speed of an associated mechanism instead of by the change of pressure in an associated receptacle. The substantially stationary contact 97 is connected with a flexible conductor 98 and it is carried by a resilient supporting strip 99 but is insulated therefrom. The resiliency of the strip 99 is sufficient to supply the necessary pressure between the contacts 91 and 46. Associated with the strip 99 either directly or indirectly is a centrifugal governor, which is operated at a speed proportionate to a machine or mechanism to be controlled. In the diagrammatic illustration there is a vertical shaft I carrying governor balls IOI, IOI which upon rotation at a speed above a predetermined maximum swing outward, and in so doing move the member I 02 upward. The member I02 in moving upward engages a shoe I03 carried by the strip 99 and thus moves the strip upward and reduces the contact pressure sufficiently to permit the movable contact 46 to move to its open-circuit position. For convenience of illustration and simplicity of description I have shown the centrifugal governor as oooperating directly with the contact supporting strip 99, but it will be understood that in practice any desired mechanical or electrical means may be interposed to effect the movement of the strip 99 as the result of the action of the centrifugal governor.

In Fig. 21 I have shown another construction wherein the automatic opening is effected by conditions entirely independent of current conditions in the circuit. The construction shown in Fig. 8 is modifled by omitting the heating coil 50, and the bi-metallic strip 49 is of such character as to be responsive to temperature changes in the ambient atmosphere. Thus the circuit breaker opens when the atmospheric temperature rises above a predetermined maximum.

I have referred to deflection of the strip 49 resulting from an increase in temperature, but it will be obvious that by differently arranging the strip a similar result can be obtained with a decrease in temperature.

In Fig. 22 I have shown a construction somewhat similar to that shown in Fig. 11, but the movable contact I1 is insulated from thebi-metallic strip I04 which carries it. It is only the strip 56 that is connected in the circuit and this will act as already described to cause the opening of the circuit upon overload. The two strips 56 and I04, instead of deflecting oppositely, as for instance downward and upward, upon an in-. crease in temperature, move in the same direction, as for instance downward. If the temperature of the surrounding atmosphere is changed, the strips deflect in the same direction, thus preventing any change in contact pressure due to temperature changes in the atmosphere. With this construction there is provided a compensation for changes in atmospheric temperature, and the automatic overload operation will be uniform and will not be influenced by external temperature.

In Fig. 23 I have shown a construction which is similar to that shown in Fig. '7 so far as concerns the operating and retaining means for the movable contact member. The substantially stationary contact I05 is carried by a bi-metallic strip I06 which is electrically connected with the contact and forms a part of the circuit. Carried by the bi-metallic strip I09 and insulated therefrom is a shoe I01. A piston rod I08 engages the shoe I0! and is connected at its upper end with a piston I09 operable in a cylinder IIO. A spring III normally holds the piston I09 against downward movement. Connected with the upper end of the cylinder IIII is a pipe II2 which serves to connect the cylinder with an associated fluid receptacle. When the current through the circuit breaker exceeds a predetermined maximum, the bi-metallic strip is deflected'downward, thus increasing the contact pressure and causing" the lug 4| to be disengaged from the detent 42. If the fluid pressure in the associated receptacle or system rises above a predetermined maximum the corresponding pressure in the upper end oi the cylinder IIII causes the piston I09 to move downward in opposition to the spring III, thus mechanically deflecting the strip I06 and causing increased contact pressure which, in turn causes the circuit breaker to open in the manner already described. It will be observed that with this construction there are two separate means each serving upon the attainment of a predetermined condition to effect the required change in the contact pressure to enable the circuit breaker to open. One of these means, that is, the bimetallic strip I09, acts automatically upon the attainment of an abnormal current condition in the circuit, and the other of these means, the piston I09 and associated parts, acts entirely independently of any current condition in the circuit and in response to an entirely external condition.

Although I have shown in Fig. 23 a construction wherein the opening of the circuit breaker is effected by an increase in contact pressure, it will be understood that a retaining means of the toggle type may be substituted and that opening of the circuit breaker may be effected by a decrease in contact pressure, such decrease being attained by an obvious re-arrangement or reversal of the described parts. It will also be understood that by reversing the positions of the spring III and the pipe II! the circuit breaker may be operated by a decrease in fluid pressure instead of by an increase.

In Fig. 24 I have shown another construction similar to the construction'shown in Figs. 3 to 6. In this construction the bodily movable bi-metallic latch I4 is retained, but it is provided with an armature I I 3 which is associated with an electromagnet II4 carried by the movable contact member and electrically connected between the strip I4 and the movable contact 8. The action of the circuit breaker will be exactly as already described in connection with Figs. 3 to 6 with the exception that upon the attainment of extreme excess current or short circuit conditions the electro-magnet II4 will cooperate with the bi-' metallic strip I4 to cause the said strip to instantly move downward and thus more quickly cause the circuit breaker to open.

In Fig. 24 I have also shown electro-magnetic means for reducing the contact pressure, this Iii means consisting of two magnets H and H6 acting on armatures carried by the respective bimetallic strips 30 and 3|. The circuit of these magnets is entirely independent of the main circuit through the circuit breaker and the magnet circuit may be controlled in any suitable way, as by means of a switch 1. The main circuit can be opened automatically as the result of abnormal current conditions in the circuit by the thermal deflecting of the strips 30 and 3 I, or by the releasing of the bi-metallic latch H; or the main circuit can be opened irrespective of the current conditions therein by independently energizing the magnets H5 and H6 and thus deflecting the strips 30 and 3|. The magnets H5 and H6 may be used to enable the circuit breaker to be opened manually by the closing of the remote switch i I! in the magnet circuit, or the said circuit may be connected directly or indirectly with any suitable device responsive to predetermined conditions so as to be energized upon the attainment of such predetermined conditions.

While I have shown in detail and diagrammatically several widely different embodiments of the invention, it will be understood that the embodiments selected are merely illustrative and that there are many other possible embodiments. In particular it is to be observed that difierent types of retaining means may be combined with different types of pressure changing means, and that I do not limit myself to the particular combinations disclosed. It will be further understood that I may use contact pressure changing means controlled by various conditions independent of the main circuit conditions, the examples illustrated in Figs. 18 to 24 being merely representative. It will be observed that with all of the constructions shown and described, the retaining means serves to automatically release the movable contact solely as the result of change in pressure. With some of the constructions, as for instance that shown in Figs. 1 to 6, release is effected as the result of decrease of pressure, and in others of the constructions, as for instance that shown in Fig. '7, release is effected as the result of increase of pressure; but in each instance the retaining means effects the release automatically and without intervention of any separately actuated trip mechanism. While I prefer to construct the retaining means in such a way that it automatically effects release solely as the result of pressure change, I do not so limit myself except as this limitation may specifically appear in the claims.

In most of the constructions shown and described, the means for changing the pressure between the contacts is associated with one of the contacts only and is entirely separate from and independent of the other contact and is entirely separate from and independent from any parts in non-separable relationship with the other contact. This is in contrast with prior art constructions wherein the variation in pressure at the contacts is effected solely by interaction of one contact or its support with the other contact or its support. More specifically, the constructions herein shown and described are to be distinguished-from prior art constructions wherein the variation in pressure at the contacts is effected solely by magnetic repulsion between the contacts or their supports. While this association of the pressure changing means solely with one contact is preferred and is shown, I do not so limit myself except as this limitation may specifically appear in the claims.

In some of the claims the means for changing the contact pressure is described as acting independently of the means for retaining the movable contact in contact engaging position. By this it is meant that the retaining means is not directly depended upon nor utilized for changing the pressure, although in some instances the retaining means normally serves to hold the pressure changing means in its operative position. An example of this is to be found in Fig. wherein the retaining means 23, 26 serves to hold the pressure changing means 58 in its operative position.

Of the several constructions disclosed, only a small number are herein specifically claimed. The right is reserved to specifically claim in divisional or continuing applications those constructions that are not herein specifically claimed.

What I claim is:

1. In a device of the class described, the combination of a contact and a support therefor, a second contact normally engaging the first contact with a predetermined pressure, one of the said contacts being movable to disengage and engage the other and being biased for disengaging movement, means additional to the said contacts and the said support for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predetermined change from the said normal pressure between the contacts and is adapted in and of itself to automatically release the said movable contact solely as the result of the said predetermined change, and means additional to the said contacts acting upon the said second contact separately from the retaining means to efiect the said predetermined change from the said normal pressure between the contacts and serving by reason of. the said pressure change to cause the said retaining means to become ineifective, the said additional means being entirely separate from and independent of the first said contact and any parts in non-separable relationship therewith.

2. In a device of the class described, the combination of a contact and a support therefor, a second contact normally engaging the first contact with a predetermined pressure, one of the said contacts being movable to disengage and engage the other and being biased for disengaging movement, means additional to the said contacts and the said support for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its eifectiveness upon the avoidance of a predetermined change from the said normal pressure between the contacts and is adapted in and of itself to automatically release the said movable contact solely as the result of the said predetermined change, and a magnet acting upon the said second contact separately from the retaining means to effect the said predetermined change from the said normal pressure between the contacts and serving by reason of the said pressure change to cause the said retaining means to become ineffective, the said magnet being entirely separate from and independent of the first said contact and any parts in non-separable relationship therewith.

3. In a device of the class described, the combination of two contacts normally engaging each other with a predetermined pressure, one of the said contacts being movable to disengage and engage the other and being biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predetermined change from the said normal pressure between the contacts. and a fluid-pressure responsive means acting separately from the retaining means to eiIect the said predetermined change from the said normal pressure between the contacts and serving by reason of the said pressure change to cause the said retaining means to become ineffective.

4. In a device of the class described, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means additional to the said contacts for normally resisting the bias or the movable contact and for retaining the said contact in engaging position which retaining means is normally dependent for its efi'ectiveness upon the avoidance of a predetermined change in the pressure between the contacts and is adapted in and of itself to automatically release the said movable contact solely as the result of the said predetermined change, a spring of the leaf type supporting one of the contacts and permitting the contact to yield as pressure is applied to effect normal contact engagement, and means additional to the said contacts and acting on the spring separately from the retaining means to change the pressure between the contacts and serving by reason of the said pressure change to render the retaining means inefiective to retain the movable contact in its engaging position.

5. In a device of the class described, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means additional to the said contacts for normally resisting the bias of the movable contact and for retaining the said contact in engaging position which retaining means is normally dependent for its eifectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and a means connectedv with one of the contacts and responsive to thermal variations so as to change the pressure between the contacts, the last said means acting separately from the retaining means and serving by reason of the said pressure change to render the retaining means inefiective to retain the movable contact in its engaging position.

6. The combination in a circuit breaking device of the class described, of two normally engaging contacts one of which is movable to disengage and engage the other and is biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its efiectiveness upon the maintenance of at least a predetermined minimum pressure between the contacts and is adapted in and of itself to automatically release the said movable contact solely as the result of reduction in contact pressure below the said minimum, and means additional to the said contacts acting upon one contact separately from the retaining means to reduce the pressure between the contacts below the said minimum and serving by reason of the pressure reduction to cause the said retaining means to become ineffective, the said additional means being entirely separate from and independent of the first said contact and any parts in non-separable relationship therewith.

'l. The combination in a circuit breaking device of the class described, of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means additional to the said contacts for normally resisting the bias of the movable contact and for retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the maintenance of at least a predetermined minimum pressure between the contacts, a spring of the leaf type supporting one of the contacts and by its reaction causing the required pressure when normal contact engagement is effected, and means additional to the said contacts and acting on the spring separately from the retaining means to reduce the pressure between the contacts below the said predetermined minimum and serving by reason of the pressure reduction to render the retaining means ineffective to retain the movable contact in its engaging position.

8. The combination in an automatic circuit breaker of two contacts one of which is movable to engage and disengage the other, the said movable contact being biased for disengaging movement but being normally held in its engaging position by reason of the normal pressure between the contacts, and a resilient bi-metallic strip connected with one of the contacts and permitting the contact to yield as pressure is applied to effect normal contact engagement, the said strip as the result of a temperature change being deflectible in the direction to reduce the pressure and thus permit the movable contact to automatically move in the disengaging direction.

9. The combination in a circuit breaking device of the class described, of two normally engaging contacts one of which is movable to disengage and engage the other and is biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its effectiveness upon the maintenance of at least a predetermined minimum pressure transmitted directly thereto from the said contacts and is adapted in and of itself to automatically release the said movable contact upon a reduction of the said transmitted pressure below the said minimum, and means additional to the said contacts acting separately from the retaining means to reduce the pressure between the contacts so that the said predetermined minimum pressure is no longer transmitted to the retaining means which thereupon becomes ineffective.

10. The combination in a circuit breaking device of the class described, of two contact supports at least one of which is movable, cooperating contacts mounted on the respective supports and one of them mounted so as to yield relatively to its support as pressure is applied to efiect normal contact engagement, means biasing the movable support for disengaging movement, means additional to the said contacts for normally resisting the bias of the movable support and for retaining the said support in position to maintain the engagement of the contacts which retaining means is normally dependent for its effectiveness upon the maintenance of at least a predetermined minimum pressure transmitted directly thereto from the said contacts, and means additional to the said contacts and upon the attainment of a predetermined condition acting separately from the retaining means to cause both contacts to move slightly in the direction to reduce the pressure on the retaining means below the said predetermined minimum and serving by reason of the pressure reduction to render the retaining means ineffective to retain the movable contact in its engaging position.

11. The combination in a circuit breaking device of the class described, of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, toggle links normally retaining the movable contact in contact engaging position which links are biased to their ineflective position and are normally held in their ei'iective position by contact pressure. and means additional to the contacts acting independently of the toggle links to reduce the contact pressure and to thereby reduce the pressure on the toggle links so as to permit them to move to their ineffective position and thus release the movable contact for automatic disengaging movement.

12. An automatic circuit breaker comprising in combination, two normally engaging contacts one of which is movable to disengage and engage the other and is biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of more than a predetermined maximum pressure between the contacts, and means acting upon one contact independently of the other to increase the pressure between the contacts above the said predetermined maximum and serving by reason of the pressure increase to cause the said retaining means to become ineil'ective.

13.An automatic circuit breaker comprising in combination, two normally engaging contacts one 01 which is movable to disengage and engage the other and is biased for disengaging move ment, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is nor mally dependent for its eiiectiveness upon the avoidance of more than a predetermined maximum pressure between the contacts, and a fluidpressure responsive means acting to increase the pressure between the contacts above the said predetermined maximum and serving by reason of the premure increase to cause the said retaining means to become ineffective.

14. An automatic circuit breaker comprising in combination, two normally engaging contacts one of which is movable to disengage and engage the other and is biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its efiectiveness upon the avoidance of more than a predetermined maxi mum pressure between the contacts, and a resilient bi-metallic strip connected with one oi the contacts and permitting the contact to yield as pressure is applied to eifect normal contact engagement, the said strip as the result oi! a temperature change being defiectable in the direction to increase the pressure between the contacts above the said predetermined maximum and serving by reason oi the pressure increase to cause the said retaining means to become ineffective.

15. In an automatic circuit breaker, the combination of a contact and a support therefor, a second contact normally engaging the first contact with a predetermined pressure, one of the said contacts being movable to disengage and engage the other and being biased for disengaging movement, means additional to the said contacts and the said support for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its eil'ectiveness upon the avoidance of a predetermined change from the said normal pressure between the contacts and is adapted in and of itself to automatically release the said movable contact solely as the result or the said predetermined change, and electro-responsive means acting upon the said second contact separately from the retaining means to effect the said predetermined change irom the said normal pressure between the contacts upon the attainment of an abnormal current condition in the circuit and serving by reason of the said pressure change to cause the said retaining means to become lnei- Iective, the said electro-responsive means being entirely separate from and independent of the first said contact and any parts in non-separable relationship therewith.

- 16. In an automatic circuit breaker, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means additional to the said contacts for normally resisting the bias of the movable contact and for retaining the said contact in engaging position which retaining means is dependent !or its effectiveness upon the avoidance of predetermined change in the pressure between the contacts, and an electro-thermally responsive means additional to the contacts which upon the attainment of excess current conditions in the circuit acts on one of the contacts independently of the retaining means to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

1'7. In an automatic circuit breaker, the combination of two contacts one 0! which is movable to engage and disengage the other and is biased for disengaging movement, means additional to the said contacts for normally resisting the bias of the movable contact and for retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and a bi-metallic strip arranged to be heated in accordance with the current conditions in the circuit and to be automatically deflected upon the attainment 0! a predetermined abnormal current condition, the said strip upon being so deflected acting on one of the contacts independently of the retaining means to eiiect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

18. In an automatic circuit breaker, the combination of two contacts one of which is movable to engage and disengage the other and one of which is mounted'so as to yield as pressure is applied to effect normal contact engagement, means biasingthe movable contact for disengaging movement, a bi-metallic strip carrying one of the contacts which strip upon the attainment of excess current conditions in the circuit is subjected to heating action which tends to deflect it and thus effect a change in the contact pressure, and means additional to the bi-metallic strip normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent tor its eiiectiveness upon the avoidance of the aforesaid change in the contact pres-- sure, the said retaining means becoming ineflective and permitting automatic disengaging movement of the movable contact when the contact pressure is sufliciently changed as the result of the heating of the bi-metalllc strip.

19. The combination in an automatic circuit breaker, of two normally engaging contacts one or which is movable to disengage and engage the other and is biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its efi'ectiveness upon the maintenance of at least a predetermined minimum pressure between the contacts and is adapted in and of'itself to automatically release the said movable contact solely as the result of reduction in contact pressure below the said minimum, and electro-responsive means additional to the said contacts and acting upon one contact separately from the retaining means to reduce the pressure between the contacts below the said-minimum upon the attainment of an abnormal current condition in the circuit and serving by reason of the pressure reduction to cause the said retaining means to become ineifective, the said electro-responsive means being entirely separate from and independent of the first said contact and of any parts in non-separable relationship therewith.

20. The combination in an automatic circuit breaker, of movable and stationary contact supports, cooperating movable and substantially stationary contacts mounted on the respective supports and one of them mounted so as to yield relatively to its support as pressure is applied to effect normal contact engagement, means biasing the movable support for disengaging movement, means additional to the said contacts for normally resisting the bias of the movable support and for retaining the said support in position to maintain the engagement of the contacts which retaining means is normally dependent for its effectiveness upon the maintenance of at least a predetermined minimumpressure transmitted directly thereto from the said contacts, and electro-responsive means additional to the contacts and serving upon the attainment of an abnormal current condition in the circuit to cause both contacts to move slightly in the direction to reduce the pressure on the retaining means below the said predetermined minimum, the said electro-responsive means acting separately from the retaining means and serving by reason of the pressure reduction to render the retaining means inefiective to retain the movable contact in its a in sition. 2 1. Th e bmbination in an automatic circuit breaker, of two contacts one of which is movable to engage and disengage the other and one oif which is resiliently mounted so as to yield as pressure is applied to efiect normal contact engagement, means biasing the movable contact for disengaging movement, toggle links normally retaining the movable contact in contact engaging position which links are biased to their ineffective position and are normally held in their efi'ective position by contact pressure resulting from the said resilient mounting, and an electroresponsive means additional to the said contacts and operable upon the attainment oi excess current conditions in the circuit and acting independently of the toggle links to reduce the contact pressure and to thereby cause the togglelinks to release the movable contact for automatic disengaging movement.

22. The combination in an automatic circuit breaker, of two contacts one of which is movable to engage and disengage the other and one of which is resiliently mounted so as to yield as pressure is applied to enact normal contact engagement, means biasing the movable contact for disengaging movement, means additional to the said contacts for normally resisting the bias of the movable contact and for retaining the said contact in engaging position which retaining means is normally dependent for its efl'ectiveness upon the contact pressure resulting from the said resilient mounting, and an electrothermally responsive means additional to the said contacts which upon the attainment of excess current conditions in the circuit acts on one of the contacts independently or the retaining means to reduce the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movemen 23. The combination in an automatic circuit breaker, of two contacts one of which is movable to engage and disengage the other and one of which is resiliently mounted so as to yield as pressure is applied to efiect normal contact engagement, means biasing the movable contact for disengaging movement, a bi-metallic strip carrying one of the contacts which strip upon the attainment of excess current conditions in the circuit is subjected to heating action which tends to deflect it in the direction to reduce the contact pressure, and means additional to the bi-metallic strip normally resisting the bias of the movable contact and retaining the said contact in engaging position which means is normally dependent for its effectiveness upon contact pressure resulting from the said resilient mounting, the said retaining means becoming inefifective and permitting automatic disengaging movement of the movable contact when the contact pressure is sufliciently reduced as the result of the heating of the bi-metallic strip.

24. The combination in an automatic circuit breaker, of two contacts one of which is movable to engage and disengage the other, means biasing the movable contact for disengaging movement, a resilient bi-metallic strip supporting one of the contacts and deflectable to permit the contact to yield as pressure is applied to effect normal contact engagement, the said strip being electrically connected in the circuit so that upon the attainment of excess current conditions therein the heating action in the strip tends to deflect it in the same direction in which it is deflected by pressure, and means additional to the bi-metallic strip normally resisting the bias of the movable contact and retaining the said contact in engaging position which means is normally dependent for its effectiveness upon pressure resulting from the resilience of the bi-metallic strip, the said retaining means being released to permit automatic disengaging movement of the movable contact when the said pressure is sumciently reduced as the result of the heating of the bi-metallic strip.

25. The combination in an automatic circuit breaker, of movable and substantially stationary cooperating contacts one of which is resiliently mounted so as to yield as pressure is applied to effect normal contact engagement, means biasing the movable contact for disengaging movement, a bi-metallic strip carrying the substantially stationary contact which strip upon the attainment of excess current conditions in the circuit is subjected to heating action which tends to deflect it in the direction to reduce the contact pressure, and means normally retaining the said contact in engaging position which means is normally Wm tially stationary cooperating contacts one of which contacts of each pair is resiliently mounted so as to yield as pressure is applied to effect normal contact engagement, means biasing the movable contacts for disengaging movement in 15 unison, two bi-metallic strips carrying the respective substantially stationary contacts which strips upon the attainment of excess current conditions in the circuit are subjected to heating action which tends to deflect them in the direcno tion to reduce the contact pressure, and means normally retaining the two movable contacts in engaging positions which means is normally dependent for its effectiveness upon contact pressure resulting from the said resilient mounting of two of the contacts, the said retaining means becoming inefiective and permitting automatic disengaging movement of the movable contacts when the contact pressure is sufllciently reduced as the result of the heating of the bi-metallic 3; strips.

:27. The combination in an automatic circuit breaker, of movable and substantially stationary cooperating contacts, means biasing the movable contact for disengaging movement, a resilient himetallic strip supporting the movable contact and deflectable to permit the said contact to relatively yield as pressure is applied to effect normal contact engagement, the said strip being electrically connected in the circuit so that upon the attain ment of excess current conditions therein the heating action of the strip tends to deflect it in the same direction in which it is deflected by pressure, and means normally retaining the movable contact in engaging position which means is normally dependent for its effectiveness upon pressure resulting from the resilience of the bi-metallie strip, the said retaining means being released to permit automatic disengaging movement of the movable contact when the said pressure is sufllciently reduced as the result of the heating of the bi-metallic strip.

28. An automatic circuit breaker comprising in combination, two normally engaging contacts one or which is movable to disengage and engage the other and is biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of more than a predetermined maximum pressure betweenthe contacts, and electro-responsive means acting upon one contact independently of the other to increase the pressure between the contacts above the said predetermined maximum.

.65 upon the attainment of an abnormal current condition in the circuit and serving by reason of the pressure increase to cause the said retaining means to become inefiective.

29. In an automatic circuit breaker, the combi- -.70 nation or two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its eflectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and two separate means additional to the said contacts and each upon the attainment of a predetermined condition acting separately from the re- 5 taining means to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

30. In an automatic circuit breaker, the com- 10 bination of two contacts one of which is movable to engage and disengage the other and one 01' which is mounted so as to yield as pressure is applied to effect normal contact engagement, means biasing the movable contact for disengaging u movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance 01 a predetermined change in the Q pressure between the contacts, and two separate means additional to the said contacts and both acting directly on one of the contacts and each upon the attainment of a predetermined condition acting separately from the retaining means a to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

31. In an automatic circuit breaker, the coma bination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position a which retaining means is normally dependent for its effectiveness upon the pressure between the contacts, and two separate means additional to the said contacts and each upon the attainment of a predetermined condition acting separately 0 from the retaining means to reduce the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

32. In an automatic circuit breaker, the com- 5 bination of two contacts one of which is movable to engage and disengage the other and one of which is resiliently mounted so as to yield as pressure is applied to effect normal contact engagement, means biasing the movable contact for 50 disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the pressure between the contacts resulting 55 from the said resillentmounting, and two separate means additional to the said contacts and acting respectively on the two contacts and each upon the attainment of a predetermined condition acting separately from the retaining means 60 to reduce the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

33. The combination in an automatic circuit breaker, of two contacts one 0! which is movable M to engage and disengage the other and is biased for disengaging movement, means normally resisting the bias or the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predeter- I mined change in the pressure between the contacts, and two separate means additional to the said contacts and each acting separately from the retaining means to effect the said predeter- 15 mined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement, one of the said pressure changing means acting automatically upon the attainment of an abnormal current condition in the circuit and the other acting entirely independently of any current condition in the circuit.

34. The combination in an automatic circuit breaker, of two contacts one oi which is movable to engage and disengage the other and one oi which is mounted so as to yield as pressure is applied to effect normal contact engagement, means biasing the movable contact for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and two separate means additional to the said contacts and both acting directly on the same contact and each acting separately from the retaining means to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement, one of the said pressure changing means acting automatically upon the attainment of an abnormal current condition in the circuit and the other acting entirely independently 0! any current condition in the circuit.

35. The combination in an automatic circuit breaker, of two contacts one of which is movable to engage and disengage the other and one of which is mounted so as to yield as pressure is applied to efle'ct normal contact engagement, means biasing the movable contact for disengaging movement, a bi-metallic strip connected with one of the contacts which strip upon the attainment of excess current conditions in the circuit is sub- Jected to heating action which tends to deflect it and thus effect a change in the contact pressure, means additional to the said bi-metallic strip also tending to change the contact pressure upon the attainment of a predetermined condition independent of current conditions in the circuit, and means separate from the bi-metallic strip normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of the aforesaid change in the contact pressure. the said retaining means becoming ineffective and permitting automatic disengaging movement of the movable contact when the contact pressure is sufliciently changed either by the thermal deflection of the bi-metallic strip or by the additional pressure changing means.

36. The combination in an automatic circuit breaker, of two contacts one of which is movable to engage and disengage the other and one of which is mounted so as to yield as pressure is applied to effect normal contact engagement, means biasing the movable contact for disengaging movement, a bi-metallic strip carrying one of the contacts which strip upon the attainment of excess current conditions in the circuit is subjected to heating action which tends to deflect it and thus effect a change in the contact pressure, means additional to the said bi-metallic strip and acting to deflect it in the direction to effect the aforesaid change in the contact pressure upon the attainment of a predetermined condition independent of current conditions in the circuit, and means separate from the bi-metallic strip normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of the aioresaid change in the contact pressure, the said retaining means becoming ineffective and permitting automatic disengaging movement of the movable contact when the contact pressure is suiliciently changed either as the result of the deflection of the bi-metallic strip by heating or as the result of the deflection thereof by the said additional means.

3'1. The combination in an automatic circuit breaker, of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its eflectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and two separate means additional to the said contacts and each acting separately from the retaining means to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement, one of the said pressure changing means being electro-responsive and acting upon the attainment of an abnormal current condition in the circuit and the other of the said pressure changing means being fluid-pressure responsive and acting entirely independently of any current condition in the circuit.

38. An automatic circuit breaker comprising in combination, two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and two separate electro-responsive means additional to the said contacts and both operable upon the attainment of a predetermined abnormal current condition in the circuit but having difierent operating characteristics, each of the said electro-responsive means acting separately from the retaining means and tending to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

39. An automatic circuit breaker comprising in combination, two contacts one of which is movable to engage and disengage the other and one of which is mounted so as to yield as pressure is applied to effect normal contact engagement, means biasing the movable contact for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and two separate electro-responsive means additional to the said contacts and both operable upon the attainment of a predetermined abnormal current condition in the circuit, one said electro-responsive means acting on one of the contacts and the other electro-responsive means acting on the other of the contacts and both means tending to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

40. An automatic circuit breaker comprising in combination, movable and substantially stationary cooperating contacts, means biasing the movable contact for disengaging movement, two resilient bi-metallic strips respectively supporting the movable and substantially stationary contacts and each deflectable to permit the corresponding contact to yield as pressure is applied to eflect normal contact engagement, the said strips being electrically connected in the circuit so that upon the attainment of excess current conditions therein the heating action in the strips tends to deflect them in the same respective directions in which they are deflected by pressure, and means normal- 1y retaining the movable contact in contact engaging position which means is normally dependent for its effectiveness upon pressure resulting from the resilience oi the bi-metallic strips, the said retaining means being released to permit automatic disengaging movement of the movable contact when the said pressure is suiiiciently reduced as the result of the heating of either or both 01' the bi-metallic strips.

41. An automatic circuit breaker comprising in combination, cooperating movable and substantially stationary contacts at least one of which is resiliently mounted so as to yield as pressure is applied to eifect normal contact engagement, means biasing the movable contact for disengaging movement, means normally retaining the movable contact in engaging position which means is normally dependent for its eflectiveness upon pressure resulting from the aforesaid resilient contact mounting and is released to permit automatic disengaging movement of the movable contact when the said pressure is suiliciently reduced, a bi-metallic strip connected with one of the contacts and arranged to be heated upon the attainment of excess current conditions in the circuitso as to be deflected in the direction to reduce the contact pressureand thereby release the retaining means, and an electro-magnet arranged to be energized upon the attainment of a predetermined abnormal current condition in the circuit and upon being so energized acting independently of the retaining means to tend to reduce the contact pressure and thereby release the retaining means.

42. An automatic circuit breaker comprising in combination. cooperating movable and substantially stationary contacts at least one of which is resiliently mounted so as to yield as pressure is applied to eii'ect normal contact engagement, means biasing the movable contact for disenga ing movement, means normally retaining the movable contact in engaging position which means is normally dependent for its eilfectiveness upon pressure resulting from the aforesaid resilient contact mounting and is released to permit automatic disengaging movement of the movable contact when the said pressure is sufllciently reduced, a bi-metallic strip carrying one of the contacts and arranged to be heated upon the attainment of excess current conditions in the circuit so as to be deflected in the direction to reduce the contact pressure and thereby release the retaining means, and an electro-magnet arranged to be energized upon the attainment of excess current conditions in the circuit and upon being so energized acting independently of the retaining means to tend to relatively move the contact other than the said strip carried contact so as to reduce the contact pressure and thereby release the retaining means.

43. In combination in an automatic circuit breaker, two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance or a predetermined change in the pressure between the contacts, and two separate electro-responsive means one operable upon the attainment oi excess current conditions in the circuit and the other operable upon the attainment oi deficient electrical energy conditions in the circuit, each of the said electroresponsive means acting independently of the retaining means and tending to effect the said predetermined change in the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

44. In combination in an automatic circuit breaker, two contacts one of which is movable to engage and disengage the other and one of which is resiliently mounted so as to yield as pressure is applied to efl'ect normal contact engagement, means biasing the movable contact for disengaging movement, means normally resisting the bias oi the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its effectiveness upon the contact pressure resulting from the said resilient mounting, and two separate electro-responsive means one operable upon the attainment of excess current conditions in the circuit and the other operable upon the attainment of deficient electrical energy conditions in the circuit, each 01' the said electro-responsive means acting independently of the retaining means and tending to reduce the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

45. In combination in an automatic circuit breaker, two contacts one of which is movable to engage and disengage the other and one oi which is resiliently mounted so as to yield as pressure is applied to eilect normal contact engagement, means biasing the movable contact for disengaging movement, means normally resisting the bias of the movable contact and retaining the said contact in engaging position which retaining means is normally dependent for its eflectiveness upon the contact pressure resulting from the said resilient mounting, and two separate electro-responsive means one operable upon the attainment of excess current conditions in the circuit and the other operable upon the attainment of deficient electrical energy conditions in the circuit, one of the said electro-responsive means acting directly on one contact and the other acting directly on the other contact and both tending to reduce the contact pressure and to thereby cause the retaining means to release the movable contact for automatic disengaging movement.

46. In an automatic circuit breaker, the combination of two contacts normally engaging each other with a predetermined pressure and one 01' them movable to disengage and engage the other and biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its eflectiveness upon the avoidance of a predetermined change i'rom the said normal pressure between the contacts, means automatically serving upon the attainment 01' a predetermined condition to effect the said predetermined change from the said normal pressure between the contacts and to thereby cause the said retaining means to become ineffective, and a separate means for automatically causing circuit-opening movement of the movable contact upon the attainment of a predetermined condition which means becomes ei'fective regardless of the pressure at the contacts and solely as the result of the last said predetermined condition.

47. In an automatic circuit breaker, the combination of two contacts normally engaging each other with a predetermined pressure and one of them movable to disengage and engage the other and biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its effectiveness upon the maintenance of at least a predetermined minimum pressure between the contacts, means automatically serving upon the attainment of a predetermined condition to reduce the pressure between the contacts below the said minimum, and a separate means for automatically causing circuit-opening movement of the movable contact upon the attainment of a predetermined condition which means becomes effective regardless of the pressure at the contacts and solely as the result of the last said predetermined condition.

48. In an automatic circuit breaker, the combination of two contacts normally engaging each other with a predetermined pressure and one of them movable to disengage and engage the other and biased for disengaging movement, means additional to the said contacts for normally retaining the said movable contact in engaging position which retaining means is normally dependent for its effectiveness upon the avoidance of a predetermined change from the said normal pressure between the contacts, current-responsive means automatically serving upon the attainment of an abnormal current condition in the circuit to effect the said predetermined change from the said normal pressure between the contacts and to thereby cause the said retaining means to become ineffective, and a separate means for automatically causing circuit-opening movement of the movable contact upon the attainment of a predetermined condition which means becomes effective regardless of the pressure at the contacts and solely as the result of the last said predetermined condition.

49. In. an automatic circuit breaker, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, manually operable mechanism including a handle for moving the movable contact to its engaging or disengaging position which mechanism is normally effective to retain the said contact in engaging position and is normally dependent for such effectiveness upon the avoidance of a predetermined change in the pressure between the contacts, a means additional to the said contacts and operable upon the attainment of a predetermined condition and acting on one of the contacts separately from the said mechanism to effect the said predetermined change in the contact pressure and to thus render the manually operable mechanism inefiective when the handle is free to move, and an electro-responsive means acting entirely independently of contact pressure for causing circuit opening movement of the movable contact upon the attainment of a predetermined abnormal current condition in the circult.

50. In an automatic circuit breaker, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, manually operable mechanism including a handle for moving the movable contact to its engaging or disengaging position which mechanism is normally effective to retain the said contact in engaging position and is normally dependent for such effectiveness upon the avoidance of a predetermined change in the pressure between the contacts, a means additional to the said contacts and operable upon the attainment of a predetermined condition and thereupon acting directly on one of the contacts separately from the said mechanism to effect the said predetermined change in the contact pressure and to thus render the manually operable mechanism ineffective when the handle is free to move, and an electro-responsive means operable upon the attainment of a predetermined abnormal current condition in the circuit and acting to release the movable contact from the control of the handle when the handle is not free to move.

51. In an automatic circuit breaker, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, manually operable mechanism including a handle for moving the movable contact to its engaging or disengaging position which mechanism is normally eifective to retain the said contact in engaging position and is normally dependent for such effectiveness upon the avoidance of a predetermined change in the pressure between the contacts, and two separate electro-responsive means additional to the said contacts and each operable upon the attainment,

of a predetermined abnormal current condition in the circuit, one electro-responsive means acting directly on one of the contacts to effect the said predetermined change in the contact pressure and to thus render the manually operable mechanism inefiective when the handle is free to move and the other electro-responsive means acting to release the movable contact from the control o1 the handle when the handle is not free to move.

52. In an automatic circuit breaker, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, manually operable mechanism including a handle for moving the movable contact to its engaging or disengaging position which mechanism is normally effective to retain the said contact in engaging position and is normally dependent for such effectiveness upon the pressure between the contacts, and two separate electro-responsive means additional to the said contacts and each operable upon the attainment of a predetermined abnormal current condition in the circuit, one electro-responsive means acting directly on one of the contacts to reduce the contact pressure and the other electroresponsive means acting to release the movable contact from the control of the handle.

53. In an automatic circuit breaker, the combination of two contacts one of which is movable to engage and disengage the other and is biased for disengaging movement, manually operable mechanism including a handle and toggle links for moving the movable contact to its engaging or disengaging position, the said toggle links being normally efiective to retain the said 

